| CPC H01J 37/265 (2013.01) [H01J 37/244 (2013.01); H01J 37/28 (2013.01); H01J 2237/221 (2013.01); H01J 2237/2443 (2013.01); H01J 2237/2801 (2013.01); H01J 2237/2814 (2013.01)] | 22 Claims |

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1. A method, comprising:
providing a modulated electrical test signal to an integrated circuit structure of a die, wherein the modulated electrical test signal has a first frequency;
applying a pulsed beam to the integrated circuit structure, wherein the pulsed beam comprises one of a frequency delta relative to the first frequency or a number of packets of beam pulses at the first frequency within each packet; and
detecting an imaging signal from the integrated circuit structure at a detector, wherein the frequency delta or the packets of beam pulses establishes a modulation of the imaging signal at a second frequency less than the first frequency and distinguishable by the detector.
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